1. Field of the Invention
Embodiments of the invention relate to an improved process for the production, processing, and functional modification of polyhydroxyalkanoates (PHAs), and specifically to processes for the production, processing, and functional modification of PHAs, wherein those PHAs may be made from carbon-containing gases and materials.
2. Description of the Related Art
Polyhydroxyalkanoates (PHAs) are thermoplastic polyesters that serve as carbon and energy storage vehicles in microorganisms. PHAs are naturally biodegradable in both aerobic and anaerobic conditions, are biocompatible with mammalian tissues, and, as thermoplastics, can be used as alternatives to fossil fuel-based synthetic plastics such as polypropylene, polyethylene, and polystyrene. In comparison to traditional petrochemical-based plastics, which are neither biodegradable nor made from sustainable sources of carbon, PHA plastics afford significant environmental benefits.
The utilization of food crop derived sugars in genetically engineered microorganism-based aqueous fermentation systems is often regarded as the most efficient and economical platform for PHA production. Specifically, sugar-based PHA production processes are capable of generating high density fermentation cultures and high PHA inclusion concentrations, and, by maximizing the cell culture density and PHA inclusion concentration therein, it is believed that carbon, chemical, and energy efficiencies are also maximized. For example, comparing a low cell and PHA concentration process to a high cell and PHA concentration process, a low concentration process requires significantly more, per given unit of PHA-containing biomass, i) energy for dewatering cells prior to PHA extraction treatment, ii) liquid culture volume, and associated chemicals, mixing energy, and heat removal energy, and iii) both energy and chemicals for separating PHA from biomass. Accordingly, whereas the sugar-based genetically-engineered microorganism PHA process yields maximized cell densities and PHA concentrations relative to low concentration processes, it is also regarded as the most carbon, chemical, energy, and, thus, cost efficient PHA production method.
Unfortunately, despite these maximized efficiency advantages, sugar-based PHA production remains more expensive than fossil fuel-based plastics production. Thus, given the apparent efficiency maximization of the high density sugar-derived PHA production process, PHAs are generally considered to be unable to compete with fossil fuel-based plastics on energy, chemical, and cost efficiency.